1. CSE 101 Lesson - 1 Number System & Program Design Sonia corraya (SOC)
Farazul H Bhuiyan
Lecturer
Dept. of CSE
BRAC University
Bangladesh
Sonia corraya (SOC)

2. This Lesson Includes Following section
Number System
Program Design & Algorithm
Flow Chart
Farazul H Bhuiyan
Lecturer
Dept. of CSE
BRAC University
Bangladesh

3. Number System How Computers Represent Data Binary Numbers
The Binary Number System
Bits and Bytes
Text Codes
Binary Number
Computer processing is performed by transistors, which are switches with only two possible states: on and off.
All computer data is converted to a series of binary numbers– 1 and 0. For example, you see a sentence as a collection of letters, but the computer sees each letter as a collection of 1s and 0s.
If a transistor is assigned a value of 1, it is on. If it has a value of 0, it is off. A computer's transistors can be switched on and off millions of times each second.
Farazul H Bhuiyan
Lecturer
Dept. of CSE
BRAC University
Bangladesh

4. Number System The Binary Number System 0 (00) 1 (01) 2 (10) 3 (11)
To convert data into strings of numbers, computers use the binary number system.
Humans use the decimal system (“deci” stands for “ten”).
Elementory storage units inside computer are electronic switches. Each switch holds one of two states: on (1) or off (0).
We use a bit (binary digit), 0 or 1, to represent the state. ON
OFF
The binary number system works the same way as the decimal system, but has only two available symbols (0 and 1) rather than ten (0, 1, 2, 3, 4, 5, 6, 7, 8, and 9).
0 (00)
1 (01)
2 (10)
3 (11)
Farazul H Bhuiyan
Lecturer
Dept. of CSE
BRAC University
Bangladesh

5. Number System
Bits and Bytes
A single unit of data is called a bit, having a value of 1 or 0.
Computers work with collections of bits, grouping them to represent larger pieces of data, such as letters of the alphabet.
Eight bits make up one byte. A byte is the amount of memory needed to store one alphanumeric character.
With one byte, the computer can represent one of 256 different symbols or characters.
Farazul H Bhuiyan
Lecturer
Dept. of CSE
BRAC University
Bangladesh

6. Number System Text Codes
A text code is a system that uses binary numbers (1s and 0s) to represent characters understood by humans (letters and numerals).
An early text code system, called EBCDIC (Extended Binary Coded Decimal Interchange Code), uses eight-bit codes, but is used primarily in older mainframe systems.
In the most common text-code set, ASCII (American Standard Code for Information Interchange), each character consists of eight bits (one byte) of data. ASCII is used in nearly all personal computers.
In the Unicode text-code set, each character consists of 16 bits (two bytes) of data
Code
Character 1 2 3 4 5 A B C D E
Farazul H Bhuiyan
Lecturer
Dept. of CSE
BRAC University
Bangladesh

7. Number System In general, N bits can represent 2N different values.
For M values, bits are needed.
1 bit  represents up to 2 values (0 or 1)
2 bits  rep. up to 4 values (00, 01, 10 or 11)
3 bits  rep. up to 8 values (000, 001, 010. …, 110, 111)
4 bits  rep. up to 16 values (0000, 0001, 0010, …, 1111)
32 values  requires 5 bits
64 values  requires 6 bits
1024 values  requires 10 bits
40 values  requires 6 bits
100 values  requires 7 bits
Decimal number system, symbols = { 0, 1, 2, 3, …, 9 }
Position is important
Example:(7594)10 = (7x103) + (5x102) + (9x101) + (4x100)
In general, (anan-1… a0)10 = (an x 10n) + (an-1 x 10n-1) + … + (a0 x 100)
(2.75)10 = (2 x 100) + (7 x 10-1) + (5 x 10-2)
In general, (anan-1… a0 . f1f2 … fm)10 = (an x 10n) + (an-1x10n-1) + … + (a0 x 100) + (f1 x 10-1) + (f2 x 10-2) + … + (fm x 10-m)
Farazul H Bhuiyan
Lecturer
Dept. of CSE
BRAC University
Bangladesh

8. Other Number System
Binary (base 2): weights in powers-of-2. Binary digits (bits): 0,1.
Octal (base 8): weights in powers-of-8. Octal digits: 0,1,2,3,4,5,6,7
Hexadecimal (base 16): weights in powers-of-16. Hexadecimal digits: 0,1,2,3,4,5,6,7,8,9,A,B,C,D,E,F
Binary
Octal
Decimal
Hexadecimal
0000
0001 1
0010 2
0011 3
0100 4
0101 5
0110 6
0111 7
1000 10 8
1001 11 9
1010 12 A
1011 13 B
1100 14 C
1101 15 D
1110 16 E
1111 17 F
Farazul H Bhuiyan
Lecturer
Dept. of CSE
BRAC University
Bangladesh

9. Number System – Base–R to Decimal Conversion
( )2 = 1    2-2 1 =
= (13.625)10
(572.6)8 = 5    = = (378.75)10
(2A.8)16 = 2   = = (42.5)10
(341.24)5 = 3     = = (96.56)10
Farazul H Bhuiyan
Lecturer
Dept. of CSE
BRAC University
Bangladesh

10. Number System – Decimal to Binary Conversion
Method 1: Sum-of-Weights Method
Method 2:
Repeated Division-by-2 Method (for whole numbers)
Repeated Multiplication-by-2 Method (for fractions)
Sum-of-Weights Method
Determine the set of binary weights whose sum is equal to the decimal number.
(9)10 = = = (1001)2
(18)10 = = = (10010)2
(58)10 = = = (111010)2
(0.625)10 = = = (0.101)2
Farazul H Bhuiyan
Lecturer
Dept. of CSE
BRAC University
Bangladesh

11. Number System – Decimal to Binary Conversion
Repeated Division-by-2 Method (for whole number)
To convert a whole number to binary, use successive division by 2 until the quotient is 0. The remainders form the answer, with the first remainder as the least significant bit (LSB) and the last as the most significant bit (MSB).
(43)10 = (101011)2
Repeated Multiplication-by-2 Method (for fractions)
To convert decimal fractions to binary, repeated multiplication by 2 is used, until the fractional product is 0 (or until the desired number of decimal places). The carried digits, or carries, produce the answer, with the first carry as the MSB, and the last as the LSB.
(0.3125)10 = (.0101)2
Farazul H Bhuiyan
Lecturer
Dept. of CSE
BRAC University
Bangladesh

12. Number System - Conversion between Decimal to other Base
Decimal to base-R
whole numbers: repeated division-by-R
fractions: repeated multiplication-by-R
In general, conversion between bases can be done via decimal:
Base-2 Base-2
Base-3 Base-3
Base-4 Decimal Base-4
… ….
Base-R Base-R
Farazul H Bhuiyan
Lecturer
Dept. of CSE
BRAC University
Bangladesh

13. Number System - Conversion between Decimal to other Base
Octal and Hexadecimal Numbers
The conversion of binary, octal and hexadecimal plays an important part in digital computers. Each octal digit corresponds to three digits and each hexadecimal digit corresponds to four binary digits. The conversion from binary to octal is easily accomplished by partitioning the binary number into groups of three each, starting from the binary point and proceeding to the left and to the right. Conversion from binary to hxadecimal is similar.
Conversion from the octal or hexadecimal to binary is done by procedure reverse to the above.
Binary-Octal/Hexadecimal Conversion
Binary  Octal: Partition in groups of 3
( )2 = ( )8
Octal  Binary: reverse
( )8 = ( )2
Binary  Hexadecimal: Partition in groups of 4
( )2 = (5D9.B8)16
Hexadecimal  Binary: reverse
(5D9.B8)16 = ( )2
Farazul H Bhuiyan
Lecturer
Dept. of CSE
BRAC University
Bangladesh

14. Program Design What is a computer program?
Simply put, a computer program is a set of detailed directions telling the computer exactly what to do, one step at a time. A program can be as short as one line of code, or as long as several millions lines of code. Typically, a program is stored as a collection of files.
Some common file types used in programs are:
Executable (.EXE) files actually send commands to the processor.
Dynamic Link Library (.DLL) files are partial .EXE files.
Initialization (.INI) files contain configuration
information for a program.
Help (.HLP) files contain information for the user.
Farazul H Bhuiyan
Lecturer
Dept. of CSE
BRAC University
Bangladesh

15. Program Design The Evolution of Programming Languages
To build programs, people use languages that are similar to human language. The results are translated into machine code, which computers understand
Programming has changed a lot since the first computers were created. They can be categorized based on how close to normal speech they are, and thus how far from the computer's internal language.
1st GL
Machine Language (1945)
2nd GL
Assembly Language (1950)
3rd GL
High Level Language (1960)
4th GL
Very High Level Language (1970)
5th GL
Natural Language (1980)
Language Types
Programming has changed a lot since the first computers were created. The original programs were very simple and straight forward compared to today's elaborate databases, word processors, schedulers, and action games.
Different computer languages have been created with which to write these increasingly complex computer programs. They can be categorized based on how close to normal speech they are, and thus how far from the computer's internal language.
Machine Languages
The language of the CPU (The central processing unit of the computer, which is the part that does the "thinking"). The lowest level language. Composed of 0's and 1's . So Machine code or machine language is a system of instructions and data executed directly by a computer's central processing unit. Machine code may be regarded as a primitive (and cumbersome) programming language or as the lowest-level representation of a compiled and/or assembled computer program.
Machine languages (first-generation languages) are the most basic type of computer languages, consisting of strings of numbers the computer's hardware can use. Different types of hardware use different machine code. For example, IBM computers use different machine language than Apple computers.
Assembly Languages
A much more readable rendition of machine language, called assembly language, uses mnemonic codes to refer to machine code instructions, rather than simply using the instructions' numeric values. Assembly languages (second-generation languages) are only somewhat easier to work with than machine languages. To create programs in assembly language, developers use cryptic English-like phrases to represent strings of numbers. The code is then translated into object code, using a translator called an assembler.
For example, on the Zilog Z80 processor, the machine code , which causes the CPU to decrement the B processor register, would be represented in assembly language as DEC B.
High-Level Languages
Use program statements - words and algebra-type expressions. Developed in the 50's and 60's. After a program is written in one of the high-level languages, it must be either compiled or interpreted. A compiler program rewrites the program into machine language that the CPU can understand. This is done all at once and the program is saved in this new form. A compiled program is generally considerably larger than the original. An interpreter program translates the program statements into machine language one line at a time as the program is running. An interpreted program will be smaller than a compiled one but will take longer to execute.
Higher-level languages are more powerful than assembly language and allow the programmer to work in a more English-like environment.
Higher-level programming languages are divided into three "generations," each more powerful than the last:
Third-generation languages
Fourth-generation languages
Fifth-generation languages
3rd Generation Language
Third-generation languages (3GLs) are the first to use true English-like phrasing, making them easier to use than previous languages.
3GLs are portable, meaning the object code created for one type of system can be translated for use on a different type of system.
The following languages are 3GLs:
FORTAN C
COBOL C++
BASIC Java
Pascal ActiveX
4th Generation Languages
= 4GL. Very high-level languages. These are results oriented and include database query languages. There are fewer options for programmers, but the programs are much easier to write than in lower level languages. These too must be compiled or interpreted.
Fourth-generation languages (4GLs) are even easier to use than 3GLs.
4GLs may use a text-based environment (like a 3GL) or may allow the programmer to work in a visual environment, using graphical tools.
The following languages are 4GLs:
Visual Basic (VB)
VisualAge
Authoring environments
Natural Languages  
5th Generation Languages. We don't really have any programming languages yet that use natural language. In such a language you would write statements that look like normal sentences. For example, instead of odd-looking code you would write "Who are the salesmen with sales over $20,000 last month?"
Fifth-generation languages (5GLs) are an issue of debate in the programming community – some programmers cannot agree that they even exist.
These high-level languages would use artificial intelligence to create software, making 5GLs extremely difficult to develop
Farazul H Bhuiyan
Lecturer
Dept. of CSE
BRAC University
Bangladesh

16. Program Design - Algorithm
An algorithm is a sequence of finite instructions, often used for calculation and data processing.
Start with a real-world problem that needs to be solved.
Convert the real-world problem into a computational problem
Develop an algorithm and use it to solve the computational problem
An algorithm is a precise list of instructions that determine what operations to perform on what pieces of data, in what order.
Lets see How to cook (make cake) ?
Farazul H Bhuiyan
Lecturer
Dept. of CSE
BRAC University
Bangladesh

18. Program Design - Pseudocode
Generic way of describing an algorithm, without use of any specific programming language. It Helps programmers to plan an algorithm. This is not an actual programming language, but may borrow syntax from popular programming languages.
Example Problem: Calculate the bill when someone buys a specific number of some item:
Pseudocode:
PROMT for number of items being purchased
READ number of items being purchased
PROMPT for price per item
READ price per item
CALCULATE subtotal
CALCULATE tax
CALCULATE total
DISPLAY total
When describing input, output, computations, etc, the following terms are often used:
Input: INPUT, READ, GET
Output: PRINT, DISPLAY, SHOW, PROMPT
Compute: COMPUTE, CALCULATE, DETERMINE
Initialize: SET, INIT
Add one: INCREMENT, BUMP
Decisions: TEST, IF/THEN/ELSE, WHILE/DO
Farazul H Bhuiyan
Lecturer
Dept. of CSE
BRAC University
Bangladesh

19. Program Design - Pseudocode
Example Problem: Calculate two childrens’ allowances, based upon cents per year old.
Known Values Rate = 75 cents per year
Inputs Ages of children
Calculations Allowance = Age x Rate
Outputs Allowances for each child
Pseudo Code Algorithm:
PROMPT for Age of Child1
READ Age of Child1
PROMPT for Age of Child2
READ Age of Child2
CALCULATE Allowance for Child1 = Age of Child1 x Rate
CALCULATE Allowance for Child2 = Age of Child2 x Rate
DISPLAY Allowance for Child1
DISPLAY Allowance for Child2
Farazul H Bhuiyan
Lecturer
Dept. of CSE
BRAC University
Bangladesh

20. Program Design - Pseudocode
Sequential:
With sequential program statements, you execute one statement after another (like steps in a list)
After step X is completed, step X+1 will be performed, until the last statement has been executed.
Every step in the list will be performed.
Each step in the list will be performed once and only once.
Farazul H Bhuiyan
Lecturer
Dept. of CSE
BRAC University
Bangladesh

21. Program Design - Pseudocode
Non - Sequential:
Programs that execute only sequential program statements are pretty simplistic.
Most programs need more flexibility in the order of statement execution.
The order of statement execution is called the flow of control.
Control statements allow the execution of statements based upon decisions.
Farazul H Bhuiyan
Lecturer
Dept. of CSE
BRAC University
Bangladesh

22. Program Design - Pseudocode
Conditional statements:
Decide whether or not to execute a particular statement or statements
Also called the selection statements or decision statements.
Pseudo code Example:
IF Hours Worked over 40
THEN DISPLAY overtime pay
ELSE DISPLAY regular pay
Loop statements:
Repeatedly execute the same statement(s) for a certain number of times or until a test condition is satisfied.
Pseudo code Example:
WHILE Population UNDER Limit DO
COMPUTE Population = Population + Births – Deaths
Conditional statements:
Also called the selection statements or decision statements.
Decide whether or not to execute a particular statement or statements
Pseudocode Example:
ELSE DISPLAY regular pay
THEN DISPLAY overtime pay
IF HoursWorked over 40
Real World Problem:
Calculate one child’s allowance, based upon 75 cents per year old if s/he is under 10, and $1 per year if 10 or over.
Known Values
BreakAge = 10
OlderRate = 100 cents per year
YoungRate = 75 cents per year
Inputs
Calculations
Age of child
Allowance
Outputs
Allowance = Age x Rate
Pseudocode Algorithm:
READ Age
PROMPT for Age
THEN CALCULATE Allowance = Age x YoungRate
IF Age less than 10
DISPLAY Allowance
ELSE CALCULATE Allowance = Age x OlderRate
Loop statements:
Repeatedly execute the same statement(s) for a certain number of times or until a test condition is satisfied.
COMPUTE Population = Population + Births - Deaths
WHILE Population UNDER Limit DO
Calculate the total allowance paid to each of three children at $1 per year old.
$1 per year
Rate 3
NumKids
Ages of children
Total Allowance paid
Set Total to 0
Set KidsPaid to 0
WHILE KidsPaid under 3 DO
CALCULATE Allowance = Age x Rate
Read Age
ADD Allowance to Total
DISPLAY Total
INCREMENT KidsPaid
Dept. of CSE
Lecturer
Farazul H Bhuiyan
Bangladesh
BRAC University

23. Flow Chart - Flow Control Design Tool
Flowchart - a graphical way of writing algorithms
Rectangle is used for calculations
Parallelogram is used for input and output
Circle is used as connector
Diamond is used as decision
Symbols are connected by arrows to represent the order of the operations

24. Flow Chart – Flow Control Symbol
Process
Alternet Process
Decision
Data
Predefined Process
Internal Storage
Terminator
Document
Manual Input
Manual Operation
Connector
Display
Stored Data
Extract - Marge

25. Flow Chart – Flow Control Symbol
Every solution starts somewhere and terminates somewhere
Every flowchart must have one start symbol and one end symbol
Start and end symbols are ovals
Start
Stop
Solution
A start symbol denotes the start of the algorithm
An end symbol indicates the algorithm has terminated

26. Flow Chart – Flow Control Symbol
Build an application that asks
User to input two numbers. Then
Calculates the sum of the two numbers
Outputs the sum.
Input first_number
Input second_number
Sum = first_number + second_number
Output Sum
Stop

27. Flow Chart – Flow Control Symbol
Allow1 = Age1 x Rate
input Age1
start
Print Allow1
stop
prompt Age1
Allow2 = Age2 x Rate
Print Allow2
input Age2
prompt Age2
Calculate two children‘s allowances, based upon 75 cents per year old.
Previous Pseudocode Algorithm:
READ Age of Child1
PROMPT for Age of Child1
READ Age of Child2
PROMPT for Age of Child2
CALCULATE Allowance for Child1 = Age of Child1 x Rate
CALCULATE Allowance for Child2 = Age of Child2 x Rate
DISPLAY Allowance for Child1
DISPLAY Allowance for Child2

28. Flow Chart – Flow Control Symbol
Start
Take 2 number from user and find out which one is a bigger number
Input first_number
Input second_number Is
first_number greater
than
second_number?
YES NO
Output first_number is bigger
Output second_number is bigger
Stop

29. Flow Chart – Flow Control Symbol
Start
Input first_number
Input second_number
Sum = first_number + second_number Is
first_number greater
than
second_number?
TRUE
FALSE
Output Sum & first_number is bigger
Output Sum & second_number is bigger
Stop

30. Flow Chart – Flow Control Symbol
Lets think about this …
Start
Write a program to output the sum of 1 to 10.
That is,
Sum =0
Number = 1
Sum = Sum + Number
Is Number < 10?
Number = Number +1
True
False
Output Sum
Stop

31. Flow Chart – Flow Control Symbol
Calculate one child’s allowance, based upon 75 cents per year old if s/he is under 10, and $1 per year if 10 or over.
Allow = Age x YoungRate
start
Print Allow
stop
prompt Age
Allow = Age x OlderRate
Age < 10
FALSE
TRUE
input Age
Previous Pseudocode Algorithm:
PROMPT for Age
READ Age
IF Age less than 10
THEN CALCULATE Allowance = Age x YoungRate
ELSE CALCULATE Allowance = Age x OlderRate
DISPLAY Allowance

32. Flow Chart – Flow Control Symbol
Calculate the total allowance paid to each of three children at $1 per year old.
start
Display Total
stop
Read Age
Calc Allowance
KidsPaid < 3
FALSE
TRUE
KidsPaid = 0
Total = 0
Add Allowance to Total
Increment KidsPaid
Prompt Age
Previous Pseudo code Algorithm:
Set KidsPaid to 0
Set Total to 0
WHILE KidsPaid < 3 DO
PROMPT for Age
READ Age
CALCULATE Allowance = Age x Rate
ADD Allowance to Total
INCREMENT KidsPaid
DISPLAY Total

33. Flow Chart – Flow Control Symbol
Start
Input N
I = 1
When I<=N
Output I
I = I+ 2
End
Write pseudo code and draw flowchart for printing Sequesnce:1,3,5,9,…. N
1. Start
2. Input N
3. Set Count = 1
4. If Count < N
4a. Yes go to Step 5
4b. No, go to Step 7
5. Print Count
6. Count = Count +2 , Go to Step 4
7. End

34. Any Question Spring 2016 Farazul H Bhuiyan Lecturer Dept. of CSE
Farazul H Bhuiyan
Lecturer
Dept. of CSE
BRAC University
Bangladesh
Spring 2016